Share Repurchase Program (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands			1 Months Ended	3 Months Ended		9 Months Ended		82 Months Ended
	Sep. 01, 2017	May 10, 2017	Nov. 07, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Nov. 07, 2017
Share Repurchase Program
Increase in authorized amount	$ 1,000,000	$ 1,000,000
Cumulative authorized amount	$ 9,800,000
Authorization effective period	3 years	3 years
Remaining balance under share repurchase program				$ 994,800		$ 994,800
Common stock repurchased, shares				2,743	367	8,047	3,673
Common stock repurchased, average price per share				$ 200.70	$ 281.04	$ 235.26	$ 261.32
Common stock repurchased, value				$ 550,530	$ 102,941	$ 1,893,068	$ 959,743
Subsequent event [Member]
Share Repurchase Program
Common stock repurchased, shares			400					65,400
Common stock repurchased, average price per share			$ 209.61					$ 135.17
Common stock repurchased, value			$ 85,200					$ 8,800,000